Pentacene-based organic thin-film transistors

Organic thin-film transistors using the fused-ring polycyclic aromatic hydrocarbon pentacene as the active electronic material have shown mobility as large as 0.7 cm²/V-s and on/off current ratio larger than 10⁸; both values are comparable to hydrogenated amorphous silicon devices. On the other hand, these and most other organic TFT's have an undesirably large subthreshold slope. We show here that the large subthreshold slope typically observed is not an intrinsic property of the organic semiconducting material and that devices with subthreshold slope similar to amorphous silicon devices are possible     

Features of ultrasonic wave propagation to identify defects in composite materials modelled by finite element method

A two-dimensional plane strain finite element model with absorbing boundary condition has been developed to investigate the ultrasonic wave propagation in isotropic and orthotropic media. It is capable of simulating the experimental pulse echo technique to obtain A-scan data, when a short duration pulse is transmitted into a domain with or without a flaw. The flaw can either be a crack or an inclusion of different material such as a Teflon insert or a resin rich zone. After performing FFT on the A-scan data, frequency domain feature analysis is done. The study provides a guideline regarding the suitability of certain harmonics sensitive to certain types of flaw. The simulation shows other important artifacts of wave propagation such as mode conversion and scattering due to the presence of flaws.     

Hinokitiol induces differentiation of teratocarcinoma F9 cells

Hinokitiol, a constituent of the wood of Chamaecyparis taiwanensis, was found to induce differentiation of teratocarcinoma F9 cells. When examined by the agar-overlay method, in which expression of plasminogen activator as a differentiation marker protein was detected, this compound exhibited a dose- and time-dependent induction. Induction of differentiation by hinokitiol occurred irreversibly and required its addition for more than 12h. Among its structure-related compounds tested, tropolone and two colchicine-related compounds exerted potent activities comparable to that of hinokitiol. These findings indicate that free tropolone structure in the molecules plays an essential role in inducing differentiation of F9 cells. Hinokitiol showed a strong inhibitory effect of DNA synthesis in very early stages of culture, suggesting that this effect may be responsible for triggering differentiation of F9 cells.     

A method for system identification using the optimality criteria optimization approach

An algorithm similar to the optimality criteria approach used in structural optimization is presented for identifying stiffnesses of structural members by using vibration test data. A set of equivalent static inertia forces are obtained from the vibration analysis using d'Alembert's principle and are used to solve the multiple displacement constraint problem. The displacement constraint values are specified based on the measured experimental modal displacement data at critical locations. The algorithm is used to find the changes needed in the stiffnesses of the elements and the distribution of nonstructural mass of the nominal analytical model to correlate the analytical and experimental data. The algorithm alternates between the vibration analysis and static analysis to find the equivalent load vector and modify the stiffnesses. The identified stiffness properties of the structural elements can be used to control and study the dynamic response of the structure.     

Direct monitoring of the calcium concentration in the sarcoplasmic and endoplasmic reticulum of skeletal muscle myotubes

Direct monitoring of the free Ca2+ concentration in the sarcoplasmic reticulum (SR) was carried out in rat skeletal myotubes transfected with a specifically targeted aequorin chimera (srAEQ). Myotubes were also transfected with a chimeric aequorin (erAEQ) that we have demonstrated previously is retained in the endoplasmic reticulum (ER). Immunolocalization analysis showed that although both recombinant proteins are distributed in an endomembrane network identifiable with immature SR, the erAEQ protein was retained also in the perinuclear membrane. The difficulty of measuring [Ca2+] in 100-1000 microM range was overcome with the use of the synthetic coelenterazine analogue, coelenterazine n. We demonstrate that the steady state levels of [Ca2+] measured with srAEQ is around 300 microM, whereas that measured with erAEQ is significantly lower, i.e. around 200 microM. The effects of caffeine, high KCl, and nicotinic receptor stimulation, in the presence or absence of external calcium or after blockade of the Ca-ATPase, were investigated with both chimeras. The kinetics of [Ca2+] changes revealed by the erAEQ were similar, but not identical, neither quantitatively nor qualitatively, to those monitored with the srAEQ, indicating that at this stage of muscle development, differences exist between SR and ER in their mechanisms of Ca2+ handling. The functional implications of these findings are discussed.     

Content of carbohydrates and trace elements in a group of non-alcoholic drinks

BACKGROUND: In order to elaborate recommendations for the dietetic care of diabetic patients and other clinical disorders we have measured the concentration of carbohydrates and trace elements in a group of non alcoholic refreshments of current use in Spain. MATERIAL AND METHODS: Thirty refreshments were classified into 10 groups. Glucose and phosphate were measured by hexokinase and reduction of phospho-molybdate methods respectively in an autoanalyzer Dax-72. Glucose and fructose were analyzed by cellulose thin-layer chromatography; glucose, fructose and sucrose by gas chromatographys. Sodium and potassium by emission spectrophotometry and calcium, magnesium, iron, copper and zinc by atomic absorption spectrophotometry. RESULTS: Light refreshments and soft drinks have no carbohydrates. Isotonic beverages, fruit juices, cool tea and non alcoholic beers had less than 10 g/dl. Tonic waters, Fanta, different coles, non alcoholic bitter and others had more than 10 g/dl. Sodium levels between 15-20 mEq/l were found in the isotonic beverages and 7-Up and levels of 7 mEq/l in the others. Potassium values between 15-40 mEq/l were found in the fruit juices, 3-4 mEq/l in Gatorade and less than 1 mEq/l in the others. CONCLUSIONS: Light refreshments and soft drinks contain low concentrations of carbohydrates and sodium. Fruit juices have high potassium concentration. Such information can be especially useful for dietetic care of diabetic patients.     

Vascular aging. Role of elastin receptor

A distinction is made between atheromatous plaque formation and arteriosclerosis, only this second process is strictly age-dependent. Interactions between lipids and constituents of the vascular wall are however involved in both processes, although by different mechanisms. The progressive increase with age of elastase activity is a second important factor in the age-dependent progression of arteriosclerosis. The fragmentation of elastic fibers produces elastin peptides, present in the circulating blood in microgram/ml conc-s, increasing in several arteriopathies. The constant presence of elastin peptides in the circulation maintains activated the elastin receptor (16) on endothelial cells producing NO* with vasorelaxing activity (18). The simultaneous production of superoxyde leads to the formation of peroxynitrate, neutralized by reduced glutathion. This process, maintained over decades may well impair the antiradical defense mechanisms of the cells and deprive the endothelium from the vasorelaxing activity of NO*. We propose therefore that the maintained activation of the elastin receptor with free radical and lytic enzyme production might well represent the initiating process underlying atherogenesis.     

Condensation polymerization of pyrogallol and benzaldehyde

Novolac-type polycondensation of benzaldehyde (B) and pyrogallol (P) has been carried out at 60°C, 75°C and 90°C and at B/P mole ratios of 1.5 and 3.0 using phosphoric acid as catalyst. The reaction follows a 2nd order rate law. By using GC consumption data of benzaldehyde and pyrogallol, kinetic parameters such as the overall rate constants, activation energies (E_a) and logA values are investigated. The activation energies for 1.5 and 3.0 B/P mole ratios are found as 62.3 kJ mol^?1 and 56.4 kJ mol^?1, respectively. The molecular weights of the resins determined by measuring intrinsic viscosities (25°C, THF) are in the range of 0.03 to 0.07 dL g^?1 at various temperatures and B/P mole ratios.     

Deep levels,electrical and optical characteristics in SnTe-Doped GaSb Schottky Diodes

The GaSb layers investigated were grown directly on GaAs substrates by molecular beam epitaxy (MBE) using SnTe source as the n-type dopant. By using admittance spectroscopy, a dominant deep level with the activation energy of 0.23-0.26 eV was observed and its concentration was affected by the Sb₄/Ga flux ratio in the MBE growth. A lowest deep-level concentration together with a highest mobility was obtained for GaSb grown at 550°C under a Sb₄/Ga beam equivalent pressure (BEP) ratio around 7, which should correspond to the lowest ratio to maintain a Sb-stabilized surface reconstruction. In the Hall measurement, an analysis of the temperature-dependent mobility shows that the ionized impurity concentration increases proportionally with the sample’s donor concentration, suggesting that the ionized impurity was introduced by an SnTe source. In addition, optical properties of an undoped p-, a lightly and heavily SnTe-doped GaSb layers were studied by comparing their photoluminescence spectra at 4.5K.